Performance Parameters and Error Sources for Translation Stages

In many industrial and scientific applications it is necessary to constrain the motion of an object with respect to a reference, such as a straight line, to a great degree of precision. High-precision translation and rotation stages are necessary tools for such applications. Precision is a relative term and, for different applications, different levels of performance and thus different types of mechanisms are required. The design goals for these mechanisms involve providing the most accurate desired path of translation with the highest possible load capacity and the lowest possible friction. Typically, designers of precision positioning tools employ dovetails, ball bearings, and roller bearings as the mechanism. For high-resolution positioning applications, such as fiber alignment, flexure mechanisms are commonly used. Each type of mechanism is designed for a specific set of applications, and what is ideal for one type of experiment might be inappropriate for another. For example, a dovetail bearing might have the load capacity to position a large collimator but not the resolution to align two optical fibers. In contrast, a flexure stage might have the resolution for fiber alignment but not the range for focusing a lens. Drive mechanisms, also designed for specific applications, are used to move the component on a positioning stage to its desired location. Three basic types of drives are used: manual, stepper-motor, and piezoelectric. Manual drives and stepper-motor drives can move components over long distances in contrast to piezoelectric transducers which move components over very short distances with high resolution. An understanding of the types of positioning and drive mechanisms with their capabilities is critical to selecting the best positioning system for an application. These topics are described in the following sections.